PHP Warning: Module 'pdo_mysql' already loaded in Unknown on line 0

Hi,

I'm running a magento site, with pdo_mysql PDO and SQLITE all enabled.

However error_log under public_html is filled with

Code:

PHP Warning:  Module 'pdo_mysql' already loaded in Unknown on line 0

There aren't duplicate entries

Code:

grep ^extension /usr/local/lib/php.ini

extension_dir = "/usr/local/lib/php/extensions/no-debug-non-zts-20060613"
extension = "pdo.so"
extension = "pdo_sqlite.so"
extension = "sqlite.so"
extension = "pdo_mysql.so"

What could it be?

Regards,

 

Thank you for the link, my google skills failed me